A DC-to-DC converter of the above type is disclosed in U.S. Pat. No. 4,184,197 (FIGS. 5 and 5a) by Slobodan M. Ćuk. Dependent on a duty cycle of an on/off control signal supplied to a switch element, the Ćuk converter can both decrease (buck) and increase (boost) an input DC voltage to an output DC voltage. With a first input terminal and a first output terminal connected to each other, the voltages at a second input terminal and a second output terminal will have opposite polarities. Its inductors have large values, such that currents flowing through the inductors have a relatively large dc component and a much smaller triangular ripple value. Thus, the currents are not periodically falling to zero and are therefore called nonpulsating.
The Ćuk converter is unsuitable for applications which require the use of inductors of small size that control an output current of the converter. A typical example of such an application is a driver for driving a back light, in particular an array of LEDs, of a light-transmissive display panel, such as an LCD panel.